The strength of the green energy that powers Kyle Rayner's DC Comics universe.
Of the seven known cosmic energies that comprise the Emotional Electromagnetic Spectrum, green energy is the one that seeks to harness its s' self-control such that they can overcome or limit the effects of fear, anger, bias, and other emotions. With self-control, a is literally able to do anything they set their mind to accomplish. This makes green energy one of the more powerful forces in the Spectrum. It also makes the s of green energy, namely the Green Lantern Corps, some of the most powerful beings in the universe. However, the strength of a Green Lantern is not measured in physical strength, speed, or durability but rather in the depth of their will.
Accordingly, the strength of a power ring construct can be distilled down to the simple formula: degree of willpower + green energy = strength of a construct, with the only variable factor being "degree of willpower." That is, the stronger a member's willpower; the more they will be able to do with green energy, and the stronger their power ring energy construct will be. One of the best illustrations of this occurred in Mark Waid and Bryan Hitch's JLA (1997) #55. There, Kyle Rayner's Green Lantern is called on to protect a city from the explosion of a nearby nuclear power plant. Not only does he protect the people from the actual blast, but also from the radiation fallout. Given that Rayner is sweating, it is likely that his construct was at the upper limit.
By way of comparison, in Gerard Jones and M.D. Bright's Emerald Dawn, #3, Hal Jordan's inexperienced Green Lantern detonates an old nuclear station as a last-ditch effort to destroy Legion. His ring's green energy was able to protect him personally, but everything else in the immediate area was vaporized. Then in Charles Soule and Paulo Siqueira's Superman/Wonder Woman #7, Clark and Diana are also forced to cause a nuclear explosion in order to close the doorway to the Phantom Zone. Superman takes the brunt of the blast and is left helpless until he is able to get sunlight and regenerate. Wonder Woman, who while shielded by Superman, nevertheless suffers some loss of abilities until she is healed by Hessia. Conversely, Rayner's ability to take to force of the blast, and protect thousands of people is a testament to his willpower, and therefore the strength of his ring's construct.
However, regardless of the overall strength of a ring bearer's willpower, they will never be able to sustain the strength of a ring's construct at its highest levels over the course of a battle or use. It's too mentally and physically draining. As a result, while strong, mentally-tough of the Green Lantern Corps might be able to do anything they want with their power ring constructs, they will not be able to do it forever. In fact, the more willpower used to create and deploy a construct, the quicker the ring bearer will lose the ability to use it, as Rayner's Green Lantern demonstrates.
